Oximes are conventionally prepared by oximating a ketone or aldehyde with an aqueous hydroxylamine-containing solution. The oxime is then recovered from the aqueous solution for further reaction, as by the halogenation processes described in U.S. Pat. Nos. 3,535,361, 3,574,536, 3,658,869 and 3,751,841. Many oximes are easily recovered from the aqueous oximation reaction mixtures because the relatively water-insoluble oxime forms a separate phase from the aqueous phase, and may be separated by decantation or the like.
Acetaldehyde oxime, also known as acetaldoxime, an important intermediate in the production of certain pesticides, cannot easily be recovered from the aqueous reaction mixture by phase separation because it is relatively water-soluble under most relevant conditions; and, when a separate layer forms containing acetaldehyde oxime, such separate layer also contains appreciable amounts of water and water-soluble impurities. One method of recovering acetaldehyde oxime from the aqueous oximation reaction mixture involves extraction with an organic solvent such as benzene. Such a method is relatively energy and capital expensive, however, because the benzene must then be distilled from the acetaldehyde oxime.
It should be appreciated that many of the known processes for further reacting oximes, and especially acetaldehyde oxime, require a dilute solution of the oxime in water or some other solvent. This is especially true for the chlorination of acetyl aldoxime with Cl.sub.2.